DFI's LANParty UT RDX200 CD-DR motherboard

THE MARKET FOR HIGH-END, enthusiast-oriented motherboards is presently dominated by NVIDIA chipsets. With few exceptions, the nForce4 has run the table for nearly a year, but that might be about to change. The recently announced Radeon Xpress 200 CrossFire chipset is finally poised to offer an alternative to SLI, and several mobo makers are lining up with boards based on the ATI's new core logic.

The first CrossFire board to become available in North America is DFI's LANParty UT RDX200 CD-DR. Designed by Oskar Wu, creator of the legendary Abit BP6, the RDX200 pairs ATI's CrossFire chipset with a myriad of extra peripherals, enough BIOS options to satiate even the most demanding overclocker, and DFI's usual dose of LANParty flair. The RDX200 is also the only Socket 939 CrossFire motherboard that's certified by ATI. Can its features and performance compare with the high-end nForce4 boards already available on the market? Read on to find out.

The RDX200 uses an all-ATI chipset, pairing the Radeon Xpress 200 CrossFire north bridge with the SB450 south bridge. On the north bridge, the Xpress 200 offers a total of 22 lanes of PCI Express. Four of those lanes are reserved for PCI-E peripherals and x1 slots, while 16 are dedicated to graphics. Like NVIDIA's original SLI chipset, CrossFire splits 16 PCI-E lanes evenly between a pair of graphics cards, giving each card eight lanes to play with. That configuration may seem less than ideal with NVIDIA's new nForce4 SLI X16 chipset delivering a full 16 lanes to each of a pair of graphics cards in SLI, but our testing hasn't shown that the extra lanes do much for performance.

If you've been keeping up with the math, you'll notice that we've only accounted for 20 of the Radeon Xpress 200 CrossFire north bridge's 22 PCI Express lanes. That's because the remaining two lanes are used as an interconnect to the SB450 south bridge. The interconnect consumes both of the south bridge's PCI-E lanes, so you won't find any extras available for other peripherals or PCI-E x1 slots. You also won't find support for 300MB/s Serial ATA transfer rates or Native Command Queuing (NCQ) in the SB450. RAID support is limited, as well, with only RAID 0 and 1 arrays supported for Serial ATA drives.

To help make up for the SB450's mediocre RAID support, DFI equips the RDX200 with an auxiliary Serial ATA RAID chip from Silicon Image. The Sil 3114 serves up an additional four Serial ATA ports and can handle RAID 0, 1, 0+1, and 5 arrays, but you won't find support for 300MB/s Serial ATA transfer rates or NCQ here, either. You will find a pokey PCI interface, forcing the Sil 3114 to compete for bus bandwidth with the RDX200's Firewire chip and its PCI-based Gigabit Ethernet controller. It's surprising to see a PCI-based GigE solution on a $200 motherboard, and frankly, a little disappointing. Fortunately, the RDX200 also sports a PCI Express GigE controller from Marvell that shouldn't be constrained by PCI bus bandwidth.

As one might expect, the crab makes an appearance on the RDX200, as well. The board uses Realtek's ALC882 High Definition Audio codec, which gives it a leg up on Socket 939 nForce4 boards that are limited to plain old AC'97 sound. I wouldn't get too excited about the HD Audio support, though. We haven't had any luck getting DVD-Audio to play back on motherboards that use the SB450, and DVD-A is where most folks will be getting their high-definition audio fix.